When a grounded desktop computer or a grounded laptop computer that is plugged into an AC power adapter is connected to a grounded external audio device such as, for example, a powered loud speaker, a ground loop is created due to the sharing of the 3-prong AC wall power plug's ground pin, by both devices. The ground loop allows a portion of a return current, which is not related to the audio signal but is nevertheless within the audible frequency range, to return to earth ground through the audio connection. In other words, some of the return current of the non-audio connection in the external device (here, the powered loud speaker unit) can pass through the return path to the audio source device, rather than passing entirely back to earth ground through the ground pin of the external device's AC wall power connection. Such interference may often be heard as a buzzing sound for example. In most cases, this interference may be reduced using a ground loop break circuit, which inserts a low value resistor, e.g. from just a few ohms to 20 ohms in series between the audio ground and the return path in the desktop computer. In addition, a differential input amplifier is used when driving the audio signal into the external device, to cancel out the potential difference in the different ground nodes.